An Optical Transport Network (OTN) is a set of Optical Network Elements (ONE) connected by optical fiber links, able to provide the functionality of transport, multiplexing, switching, management, supervision and survivability of optical channels carrying client signals. OTN was designed to provide support for optical networking using wavelength-division multiplexing (WDM). ITU-T Recommendation G.709 is commonly called Optical Transport Network (OTN) (also called digital wrapper technology or optical channel wrapper). The ITU's Optical Transport Network (OTN), as defined by recommendation G.709, provides a network-wide framework that adds SONET/SDH-like features to WDM equipment (also known as Wavelength Switched Optical Network equipment, or WSON equipment). It creates a transparent, hierarchical network designed for use on both WDM/WSON devices and TDM devices. Two switching layers are formed (TDM and WSON) and functions of transport, multiplexing, routing, management, supervision, and survivability are defined. As of December 2009 OTN has standardized the line rates using Optical Transport Unit (OTU) frames, OTUk (k=1/2/2e/3/3e2/4). The OTUk is an information structure into which another information structure called Optical Data Unit (ODU) k (k=1/2/2e/3/3e2/4) is mapped. The ODUk signal is the server layer signal for client signals. At a basic level, G.709 OTN defines a frame format that “wraps” data packets, in a format quite similar to that of a SONET frame. There are six distinct layers to this format.
OPU: Optical Channel Payload Unit. This contains the encapsulated client data, and a header describing the type of that data. It is analogous to the ‘Path’ layer in SONET/SDH.
ODU: Optical Data Unit. This level adds optical path-level monitoring, alarm indication signals and automatic protection switching. It performs similar functions to the ‘Line Overhead’ in SONET/SDH.
OTU: Optical Transport Unit. This represents a physical optical port (such as OTU2, 10 Gbps), and adds performance monitoring (for the optical layer) and the FEC (Forward Error Correction). It is similar to the ‘Section Overhead’ in SONET/SDH.
OCh: Optical Channel. This represents an end-to-end optical path.
OMS: Optical Multiplex Section. This deals with fixed wavelength DWDM (Dense Wavelength Division Multiplexing) between OADMs (Optical Add Drop Multiplexer).
OTN transport and switching solutions need the capability to process lower order ODUs individually. Several lower order ODUs are time multiplexed into a higher order ODU using standard multiplexing procedure recommended in ITU G709. For example, an OTU4 signal can potentially carry 80 multiplexed flows of lower level ODU0 signals. As this signal is transported in an OTN network, it becomes necessary to observe and process the lower order ODU signal to meet the operation, administration, and management requirements of the network.
The transformation of signals from one form to another (e.g., data interleaving, space to time, etc.) is common in many datapath designs in the telecommunications field. These are generally area and power intensive, and the complexity of their implementation increases non-linearly with increasing data rates.
More specifically, in many designs, certain blocks of the datapath might handle data in a context-switched fashion, while other blocks of the datapath might handle data on an independent per-flow basis. A “context-switched fashion” and an “independent per-flow basis” refer to design options that serve multiple contexts at a time. For example, given 10 client flows that are to be processed, there are two options for processing the client flows. The first option is to have 10 processing engines, one for each flow, that are running at the rate required to process a flow. This is referred to as processing on an “independent per-flow basis.” The second option is to have a single processing engine that can process at 10 times the speed required to process the client flows and which can be time-sliced so that each flow would get a turn for the required processing. This option is referred to as processing in a “context-switched-fashion.”
The datapath uses space-to-time transformations at the interface of such blocks. Traditional space-to-time transformations have been designed using large multiplexers and delay elements. However, these designs do not scale well due to the increasing data rate and the subsequent increase of data-bus widths (these increase the power/area considerations). The number of flows that need to be independently supported is also increasing, which adds another dimension of complexity to the design of the datapath.
These issues are preventing such functions from being implemented in even the largest of the present generation of field programmable gate arrays (FPGAs) and necessitate a better design. For example, FPGAs that process data at rates of 100 gigabytes per second (gbps) and above, may be larger and consume significantly more power than FPGAs currently operating at lower data rates.
Accordingly, there is a need for systems, apparatus, and methods that improve upon conventional approaches including the improved methods, system and apparatus provided hereby.